H. A. Phillips & Co. of Chicago, Ill., assignee of this application, has long been a leader in the design, development and installation of industrial type refrigeration systems. A pioneer in recirculating systems, its engineers have constantly sought new and improved refrigeration systems and equipment. Systems and components for refrigeration which have been developed at Phillips include Phillips Pat. No. 2,570,979; Phillips Pat. No. 2,589,859; Phillips Pat. No. 2,641,281; Richards Pat. No. 2,841,962; Richards et al Pat. No. 2,871,673; Ross Pat. No. 2,966,043; and Ross Pat. No. 3,315,484. Of course, research and development continues toward more efficient yet less expensive systems.